Fish’s Position

In moving water, fish face upstream. Before planning an approach take into
account the fishes’ location in terms of its exact position and
depth. Its’ depth determines the window size that a fish views the
outside world. A fish holding close to the surface has a much smaller
window to see through than a deeply holding fish.

Approaching a shallow fish is easier than a deep one. The smaller the
window the less likely a fish can see you. Try hiding from the fish by
staying outside of its vision window. They are overly cautious to
vibrations

sensed by their lateral lines. However, shallow holding fish may be more
alert because they are more vulnerable to predators and will streak for
cover at the slightest provocation.